S&C Electric Company 121150R4 SM-4 Refill Unit

S&C Electric Company 121150R4 SM-4 Refill Unit is a high‑voltage fuse element designed for use in SM‑4 and SML‑4 holders. It is rated for 7.2 kV nominal (8.3 kV maximum) with a 100E current rating, making it suitable for coordinating protection in medium‑voltage distribution circuits. As part of S&C’s SM‑4 refill family, this unit mates with compatible SM‑4 and SML‑4 assemblies and carries cross‑references such as 251150R4 and 122150R4 to support different mounting configurations. Common applications include substations and distribution feeders that rely on replaceable fuse elements for protection and fast clearing in high‑voltage switchgear.